This invention relates to improvements in yo-yos and methods for their manufacture.
This invention relates to yo-yos, including, but not limited to high performance yo-yos as described in my U.S. Pat. No. 4,895,547 entitled Superior Performance Yo-Yo. Such high performance yo-yos are adapted to spin or xe2x80x9csleepxe2x80x9d for extended periods of time, to permit lengthy and extended tricks to be performed before the yo-yo is wound up on its string.
Although the yo-yo construction described in my ""547 patent achieves its intended objects, it would be desirable to make further improvements in its construction as well as to achieve further assembly and manufacturing efficiencies. The yo-yo is formed from a pair of injection molded plastic yo-yo halves in a conventional insert molding process in which a HeliCoil internally threaded insert, to which the yo-yo axle will attach, is placed in the mold. The mold then is closed and the plastic is injected into the mold to form the yo-yo half with the threaded insert embedded within the yo-yo half. Such conventional insert molding techniques include the use of core pins within the mold on which the inserts can be placed so that they will be located properly and in registry within the mold during the injection process. The inserts are selected from materials that are softer than those of the mold to avoid the possibility of the mold becoming damaged should an insert be improperly loaded or misaligned and the mold closed under such circumstances. Yo-yos that have been manufactured incorporating the invention described in my ""547 patent are commercially available from Yomega Corporation typically have used relatively soft inserts such as those formed from brass. Another inefficient result of making such yo-yos with conventional insert molding techniques is that in the event that a molded plastic yo-yo half is not properly formed it cannot, as a practical matter, be recycled and remolded because of presence of the embedded brass insert. The rejected yo-yo half must be discarded together with the insert. Even with a moderate rejection rate, when such yo-yos are manufactured in very large quantities, the aggregate cost of the lost plastic and insert can become a significant cost factor.
Also among the difficulties that may be encountered with the prior yo-yos is that where the threaded inserts are relatively soft as compared to the steel from which the axle of the yo-yo is formed, there may be some tendency for the threads between the axle and the insert to become stripped should the yo-yo be overtightened by the user. Should the threads become stripped, the yo-yo is no longer usable.
The yo-yo construction described in my ""547 patent, made with insert molding techniques, typically requires that the mold be operated manually by an operator. The inserts are loaded manually onto the core pins. The mold then is closed and locked. The injection step then is performed and monitored. The mold then is opened to remove the molded products, at which time the process is repeated. The procedure necessarily is subject to human error and, also necessarily results in substantial unused mold time when the mold is opened, re-loaded with inserts and closed during the insert loading process.
It would be desirable to provide a yo-yo construction and technique for its manufacture that avoids the above difficulties.
In the present invention, the yo-yo halves are molded without placing inserts in a mold cavity. The use of insert molding is made unnecessary. Consequently, the yo-yo halves can be made on continuous automated injection molding machinery with substantial higher production capability and operator efficiency than with insert molding. The yo-yo halves are molded to include a socket aligned with the central axis of the yo-yo half. The socket is open at a face of the yo-yo half, defining an insertion end, and is polygonal in cross section. The socket is relatively deep and is adapted to receive, in an interference fit, a similarly shaped threaded insert, by press fitting the insert into the socket. The socket is formed with a shallow registration socket adjacent its insertion end that is slightly larger in cross-section than the socket but having a shape to facilitate orientation and alignment of the nut with the polygonal socket. With the nut being properly aligned with the socket, the nut then can be press fitted into the socket. The polygonal configuration of the socket and nut assure that the nut cannot become loosened within the plastic. Additionally, by attaching the nut to the yo-yo half in a separate procedure, after the yo-yo half has been molded, the nut can be formed from the same material as the yo-yo axle, e.g., steel, so that there is less risk of the connecting threads being stripped.
It is among the objects of the invention to provide an improved yo-yo construction that avoids the limitations of insert molding techniques; to provide a yo-yo construction in which the axle of the yo-yo is threaded into an insert in each of the yo-yo halves where the inserts are formed from the same or like materials, and to provide an improved process for manufacturing such yo-yos.